Apple TV iOS 5.1 firmware brings new features such as support for Shared Photo Streams, ability to send audio content from Apple TV to AirPlay-enabled speakers and devices, and the ability to save multiple iTunes accounts and switch between them quickly.

AirPlay – Send audio content from Apple TV to AirPlay-enabled speakers and devices (including AirPort Express and other Apple TVs). Also includes the ability to require an onscreen code to use AirPlay with your Apple TV.